Currently, the number of data networks and the volume of traffic these networks carry are increasing at an ever increasing rate. The network devices making up these networks generally consist of specialized hardware designed to move data at very high speeds. Typical asynchronous packet based networks, such as Ethernet or MPLS based networks, are mainly comprised of end stations, hubs, switches, routers, bridges and gateways. A network management system (NMS) is typically employed to provision, administer and maintain the network.
It is common for many networks to provide some form of protection in the event of failure. For example, in the event of a link or node failure, the network can be adapted to switch data traffic around the failed element via a protection route.
A network diagram illustrating restoration in an example prior art optical network is shown in FIG. 1. The example network, generally referenced 10, comprises a plurality of nodes 14, labeled 1 through 6, end stations 12, labeled A and B and Network Management System (NMS) 24. The nodes are connected to each other via physical links 22. A path is established between end stations A and B via nodes 1, 2, 3 and 4 as represented by the dashed line 16.
In the event of a failure (e.g., fiber cut) in link 20, it is desirable to be able to switch traffic as quickly as possible to an alternate route. In this case, the alternate route for the connection between nodes 2 and 3 comprises the path that runs around the ring in the opposite direction connecting nodes 2 and 3, represented by dotted line 18. A disadvantage of this approach, however, is that the alternate path must traverse the entire ring just to bypass a failed link.
Link protection in a Wave Division Multiplexing (WDM) or Dense WDM (DWDM) optical network can be achieved by calculating and configuring a restoration path (which is the alternate route for that link) using logical links. Each physical fiber comprises many wavelengths (i.e. colors) of light wherein each color is used in a different logical link. The restoration path route calculation for the failure of any given link can be performed using the available logical links.
A disadvantage of this approach, however, is that the alternate route calculated to bypass the failed link may include a logical link that runs over the physical fiber link that failed, rendering the alternate route unusable. Search algorithms typically only have a logical view of the network since the physical network is difficult to determine. Thus, the search algorithms are not aware of the physical fiber connectivity in WDM networks. The search algorithm therefore may route the path over logical links that pass through the failed physical fiber. In the event of a fiber cut, the backup path cannot be used. This occurs because the entity calculating the protection route (restoration route) only sees the logical links (i.e. other wavelengths) as alternative routes that can be used in the event of a fiber cut. This, however, is problematic if the backup path traverses the same physical link as the link to be backed up.
Thus, there is a need for a link protection path setting mechanism for use in optical networks that is capable of calculating network protection paths for links that do not traverse same physical fiber link as the link to be backed up.